No Time? This Is How Much HIIT You Need to Reap Benefits

Can You Benefit from Just 30 Minutes of HIIT a Week?

Photo: Pond5

You know about interval training and its siblings Tabata and HIIT (high-intensity interval training). These fast-paced, sweat-inducing workouts promise to push you to your max, yielding major calorie burn and impressive health benefits. But do you really need to slog through 30-minute workouts, five times a week, to see results? Science has found that high-intensity workouts can improve cardiovascular function, blood glucose levels and respiratory fitness. But what the research has yet to discover is how often and at what intensity these benefits start occurring.

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What’s the Minimal Amount of Exercise You Can Do?

In an effort to nail down the least amount of HIIT you can do, Canadian researchers asked 14 healthy, but overweight and sedentary men and women to do a 10-minute stationary bike workout three times a week. “We wanted to push the envelope and see how low can you go [in terms of workout time],” says study co-author Martin Gibala, PhD, a professor and chair of the department of kinesiology at McMaster University in Ontario, Canada.

For three 20-second intervals, participants would push their bodies to 110 percent “all-out” effort — pedaling as fast as they could, at maximum resistance. The workout looked like this:

  • 2 minutes of warm up (biking without resistance at an easy pace)
  • 20 seconds of all-out effort
  • 2 minutes of recovery
  • 20 seconds of all-out effort
  • 2 minutes of recovery
  • 20 seconds of all-out effort
  • 3 minutes of recovery (biking without resistance at a moderate pace)

Three minutes of “all out” effort a week isn’t a lot. Yet, after doing this workout for six weeks, the subjects walked away with three important health outcomes:

Improved cardio-respiratory fitness
Yes, this is a fancy word for better overall physical fitness. In the lab, this is measured as VO2 max, or the maximum amount of oxygen you can consume when breathing. After six weeks, cardiorespiratory fitness increased by 12 percent among participants, which equates to about a 15 percent reduced risk of conditions such as heart disease, Dr. Gibabla says.

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Healthier muscles
By performing biopsies, researchers were able to measure the amount of mitochondria present in participants’ muscle cells. Mitochondria are the energy production centers of cells — the more you have, the healthier the muscle. After six weeks, researchers saw more mitochondria in the subjects’ muscles. Muscle health is underrated; unhealthy muscles are less able to help the body process insulin, which can lead to insulin resistance, a precursor to diabetes.

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Lower blood sugar and blood pressure
In the 24 hours after a workout, blood sugar levels among male participants were lower than before training. “We only saw blood sugar benefits in the men,” Dr. Giabala says. Why? There can be a number of reasons why women didn’t experience better blood sugar control, all of which — including hormones — were not controlled for in this study. However, researchers did notice a decrease in blood pressure among all subjects.

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The Benefits of All-Out HIIT Training

But how do these health outcomes measure up to those seen in longer workouts? “Short, very intense efforts can be very effective. The changes that we saw in this recent six-week study — with respect to cardiorespiratory fitness and the increase in mitochondrial content — are comparable to what we have seen in our earlier interval training studies of similar duration that involved longer protocols.” Dr. Giabala says.

The results are good — but even a workout this short can be taxing. “This way of training can be very uncomfortable,” Dr. Giabala warns. If you can handle going at 110 percent (and, in full disclosure, possibly feeling a bit sick afterward), try this workout on your own. Do it on a spinning bike, or even while swimming or running (alternate sprinting with walking), but the key is to go balls to the wall. “You shouldn’t be able to do more than 20 seconds,” Dr. Giababla advises. He also warns that if you are have heart issues, or are dealing with any other health problems, this isn’t the workout for you. Talk to a healthcare professional about whether lower-intensity training might be a better choice.

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